Tinnitus is characterized by an auditory sensation in the absence of external sound. Approximately 12 million individuals in the United States have some degree of tinnitus. About 5 million of these sufferers have severe tinnitus that interferes with their daily activities and their quality of life. In fact, severe tinnitus can lead to depression and other mental health challenges that severely affect the patient and the patient's family members. Therapies such as masking, sound therapy, electrical stimulation, and drugs have shown some benefit. Unfortunately, these treatments are non-specific and are insufficient to reverse the brain changes that cause tinnitus. Therefore, treatment of tinnitus remains a significant unmet need.
Numerous therapies have been used to treat or alleviate the symptoms of tinnitus. For example, pharmaceutical therapies such as antidepressants, anti-anxiety medications, as well as other medicinal compounds have been attempted. Neurostimulation techniques including transcranial magnetic stimulation and cortical stimulation have been used to alleviate symptoms. Sound has been used in several ways, including masking therapy auditory exposure and frequency discrimination training.
U.S. Patent Application Publication 2007/0027504 (Barrett) describes a system for treating tinnitus using vagus nerve stimulation. A patient's vagus nerve was stimulated as the patient experienced tinnitus symptoms to temporarily alleviate the symptoms. No audible tones are specifically presented or paired in Barrett's therapy.
U.S. Pat. No. 6,990,377 (Gliner) describes a therapy to treat visual impairments. The therapy includes presenting various types of visual stimuli in conjunction with stimulation of the visual cortex. The therapy described in Gliner does not control the timing relationship of the stimuli and the stimulation.
U.S. Patent Application Publication 2007/1079534 (Firlik) describes a therapy having patient interactive cortical stimulation and/or drug therapy. The therapy has patients performing tasks, detecting patient characteristics, and modifying the stimulation depending on the detected patient characteristics. The therapy described in Firlik does not control the timing relationship between the tasks and the cortical stimulation.
It is common in the prior art to suggest that stimulation of the cortex, the deep brain, the cranial nerves, and the peripheral nerves are somehow equivalent or interchangeable to produce therapeutic effects. Despite these blanket statements, stimulation at different parts of the nervous system is not equivalent. It is generally understood that the vagus nerve is a nerve that performs unique functions through the release of a wide array of neuromodulators throughout the brain. To generate certain kinds of plasticity, the timing of the stimulation of the vagus nerve is critical in producing specific therapeutic effects.
U.S. Pat. No. 6,104,956 (Naritoku) is representative of work done using vagus nerve stimulation (VNS) to treat a variety of disorders, including epilepsy, traumatic brain injury, and memory impairment. The VNS is delivered without any other therapy. To improve memory consolidation, VNS is delivered several minutes after a learning experience. Memory consolidation is unrelated to the present therapy for treating tinnitus.